title: Prospective respiratory gated carbon nanotube micro computed tomography.
abstract: OBJECTIVE
  Challenges remain in the imaging of the lungs of free-breathing mice. Although computed tomographic (CT) imaging is near optimal from a contrast perspective, the rapid respiration rate, limited temporal resolution, and inflexible x-ray pulse control of most micro-CT scanners limit their utility in pulmonary imaging. Carbon nanotubes (CNTs) have permitted the development of field emission cathodes, with rapid switching and precise pulse control. The goal of this study was to explore the utility of a CNT-based micro-CT system for application in quantitative pulmonary imaging.
  
  
  METHODS
  Twelve CB57/B6 mice were imaged during peak inspiration and end-exhalation using the CNT micro-CT system. The respiratory trace was derived from a sensor placed underneath the abdomen of the animal. Animals were allowed to breathe freely during the imaging under isoflurane anesthesia. Images were reconstructed using isotropic voxels of 77-μm resolution (50 kVp, 400 projections, 30-ms x-ray pulse). Lung volumes were measured with region-growing techniques and thresholds derived from the surrounding air and soft tissues. Basic functional parameters, including tidal volume, functional reserve capacity and minute volume, were also calculated.
  
  
  RESULTS
  The average scan time was 13.4 ± 1.8 minutes for each phase of the respiratory cycle. Mean lung volumes at peak inspiration and end-expiration were 0.23 ± 0.026 and 0.11 ± 0.024 mL, respectively. The average minute volume was 11.93 ± 2.64 mL/min.
  
  
  CONCLUSIONS
  The results of this study demonstrate the utility of a CNT-based micro-CT system in acquiring prospectively gated images from free-breathing mice for obtaining physiologic data. This technique provides an alternative to breath-hold techniques requiring intubation and offers greater dose efficiency than retrospective gating techniques.
authors.affiliation: Department of Radiology, University of North Carolina, Chapel Hill, 27599, USA. yueh@alum.mit.edu
authors.forename: Yueh Z
authors.initials: YZ
authors.lastname: Lee
authors.forename: Laurel M
authors.initials: LM
authors.lastname: Burk
authors.forename: Ko-han
authors.initials: KH
authors.lastname: Wang
authors.forename: Guohua
authors.initials: G
authors.lastname: Cao
authors.forename: Jonathan
authors.initials: J
authors.lastname: Volmer
authors.forename: Jianping
authors.initials: J
authors.lastname: Lu
authors.forename: Otto
authors.initials: O
authors.lastname: Zhou
mesh_terms: D000818:Animals; D005260:Female; D008168:Lung / Q000000981:diagnostic imaging*; D051379:Mice; D008810:Mice, Inbred C57BL; D037742:Nanotubes, Carbon; D012119:Respiration; D013990:Tidal Volume; D014057:Tomography, X-Ray Computed
chemical_list: D037742:Nanotubes, Carbon